Develops criteria to establish whether a second language (L2) speaker has achieved native-like proficiency. The study compares the performance of near-native speakers of English, non-native speakers, and controls on two tasks designed to tap aspects of Universal Grammar claimed to be subject to critical period effects. Findings reveal that native-like competence in an L2 is achievable, even by older L2 learners. (51 references) (Author/CK)